Method of preparing catechol diacetates

ABSTRACT

WHERE R1, R2, R3 and R4 are as heretofore defined, with acetic anhydride, preferably in admixture with acetic acid, in the presence of boron trifuloride etherate, subsequently contacting the resultant mixture with concentrated sulfuric acid.   WHERE R1, R2, R3 and R4 are hydrogen or alkyl comprising contacting 2-acetoxycyclohexanone of the formula:   A method of preparing a catechol diacetate of the formula:

United States Patent Mahmoud S. Kablaoui Wappingers Falls, N.Y.

[72] Inventor [2]] Appl. No. 15,299

[22] Filed Feb. 27, 1970 [45] Patented Nov. 30, 1971 [73] AssigneeTexaco Inc.

New York, N.Y.

[54] METHOD OF PREPARING CATECHOL OTHER REFERENCES Doering et al., J.Am. Chem, Soc., Vol. 71, pages 222l2226(l949) Primary Examiner-James A.Patten Attorneys-Thomas H. Whaley, Carl G. Ries and Robert A.

Kulason ABSTRACT: A method of preparing a catechol diacetate of theformula:

where R, R R and R are hydrogen or alkyl comprising conin qete yeehseerw fifilerme!9;,

if R 0C CH:

where R, R R" and R are as heretofore defined, with acetic anhydride,preferably in admixture with acetic acid, in the presence of borontrifuloride etherate, subsequently contacting the resultant mixture withconcentrated sulfuric acid.

BACKGROUND OF lNVENTlON The invention relates to the preparation ofalkylated and nonalkylated catechol diacetates.

The catechol diacetate products contemplated herein are readilyconverted by standard hydrolysis techniques to nonalkylated catechol andalkylated catechol, the former useful in pharmaceutical manufacture andthe latter as dispersants in drilling muds.

In the past, preparation of dihydroxybenzene compounds via aromatizationof ketonic compounds had been disappointing particularly in the are ofobtaining satisfactory yields in a reasonable period of time. One priormethod called for contacting cyclohexanediones with a palladiumon-carboncatalyst and in another similar procedure Raney nickel in a sodiumhydroxide solution was employed as the catalytic material. In eithersituation the yields were poor.

u mam R4 -opcm WA a..- was, where R, R, R and R are hydrogen or alkyl offrom one to 20 carbons is prepared by first contacting a2-acetoxycyclohexanone of the formula:

H OCCH;

where R, R", R and R are as heretofore defined with acetic anhydride andboron trifluoride etherate [BF .(C,H O] at a temperature between about30 and 500 C., preferably between about 80 and 150 C., and in theadditionally preferred presence of acetic acid utilizing a mole ratio ofsaid acetic anhydride to said acetoxycyclohexanone of at least about 1:1and up to l00:l or more, preferably between about 5:l and 20: l theexcess acetic anhydride functioning as reaction diluent. When employed,acetic acid normally constitutes between about 30 and 70 wt. percent ofthe reaction mixture. The reaction time is desirably about 0.5 hours and2 hours or more. The resultant reaction mixture is subsequentlycontacted with concentrated sulfuric acid at a temperature between about30 and 500 C., preferably between about 80 and 150 C., utilizing a moleratio of said sulfuric acid to said acetoxycyclohexanone of at leastabout 0.05:! and 5: l preferably between about lzl and 2: l. Thereaction period in the second contacting is of the same scope as in thefirst contacting. In the final analysis, however, reaction time undercommercial conditions will be dictated by the economics of yield versustime. Superatmospheric pressure is contemplated at temperatures abovethe boiling point of one or more of the reaction ingredients.

Both the first and second stages of the reaction are advantageouslyconducted under conditions of agitation in order to facilitate contactand further are advantageously conducted -facilitate ingredient contactand product recovery diluent may be employed. Suitable examples of suchdiluents are excess acetic anhydride or other volatilizable solventssuch as toluene, benzene, heptane, hexane, chloroform, carbontetrachloride, chlorobenzene and cyclohexane. The diluents (if employed)normally constitute between about 25 and wt. percent of the reactionmixture.

The catechol diacetate product can be recovered from the resultantreaction mixture by standard means. One such means of recovery comprisesfirst removing excess acetic anhydride and acetic acid via fractionaldistillation, quenching the residue in water wherein the water contentin the resultant quenched mixture is between about 1 and 50 wt. percent,said quenching conducted at a temperature desirably between about 0 and50 C., extracting the aqueous mixture with a water immiscible,volatilizable solvent for the catechol diacetate, washing the solventlayer with an aqueous alkali base, e.g., 0.1 to 7 wt. percent aq. sodiumbicarbonate, subjecting the washed solvent solution to fractionaldistillation to remove the volatilizable solvent leaving the catecholdiacetate as residue.

The conversion of the catechol diacetate product to the correspondingcatechol compound can be accomplished by established hydrolysistechniques such as contacting the catechol diacetate with aqueousmineral acid (e.g., 0.1 to 1 wt. percent aq. HCI utilizing a catecholdiacetate to aqueous acid weight ratio of between about 1:2 and 1:100 ata temperature between about 30 and 100 C., most preferably under refluxconditions, followed by extracting the formed dihydroxybenzene from theaqueous acid solution with a water immiscible, volatilizable solvent forthe resultant catechol compound and separating the dihydroxybenzeneproduct from the solvent in the manner outlined in respect to therecovery of the catechol diacetate.

In regard to the material features of the invention, elimination of anyof the materials or step sequence as defined either result insubstantially reduced yields or no yield of the desired catecholdiacetate product. For example, deletion of boron trifiuoride etheratefrom the first stage reaction results in a manifold decrease in yield offinal diacetate product. Further,

elimination of the preferred acetic acid component results in a decreasein yield. Still further, elimination of the employment of sulfuric acidand acetic anhydride renders the process inoperative. Still further,when 3-acetoxycyclohexanone or substituted 3-acetoxycyclohexanone wastreated as above, no diacetoxybenzene or substituted diacetoxybenzene isobtained.

By the term concentrated sulfuric acid" hereinbefore and hereinafterrecited an acid composition consisting of between and wt. percent H 80and between 0 to 5 wt. percent H O is intended.

Examples of the volatilizable selective solvents for the diacetate andcatechol products contemplated herein are ether, benzene, chloroform andcarbon tetrachloride.

Examples of the 2-acetoxycyclohexanone reactant contemplated herein are2-acetoxycyclohexanone, 2-acetoxy-4- methylcylcohexanone,Z-acetoxy-3-hexylcyclohexanone, 2- acetoxy-S-pentylcyclohexanone and2-acetoxy-3,4,5,6- tetramethylcyclohexanone. Corresponding catecholdiacetate products are catechol diacetate, 4-methylcatechol diacetate,3-hexylcatechol diacetate, S-pentylcatechol diacetate and3,4,5,6-tetramethylcatechol diacetate. Corresponding dihydroxybenzenederivatives are catechol, 4-methylcatechol, 3-hexylcatechol,S-pentyleatechol and 3,4,5,6-tetramethylcatechol.

The acetoxycyclohexanone reactants can be prepared by acylatingcyclohexanone; e.g., by contacting cyclohexanone with acetic anhydridein the presence of catalytic amounts (between about 0.0l and 0.5 wt.percent) of concentrated sulfuric acid at between about 30 and C.,desirably in the presence of solvent such as excess acetic anhydride orxylene to form a l-cyclohexenyl acetate intermediate. The formed 1-cyclohexenyl acetate is then epoxidized, e.g., by contacting theperbenzoicacid to form l-acetoxy-l ,2-epoxycyclohexana in the presenceof catalyst such as molybdenum, vanadium or tungsten catalyst, e.g.,molybdenum hexacarbonyl and in the additional presence of benzene orother suitable solvents. The 1-acetoxy-1,Z-epoxycyclohexanoneintermediate upon heating, e.g., between about 30 and 100 C. decomposesinto the desired Z-acetoxycyclohexanone. The epoxidation-cleavage ofcyclohexenylacetate to 2-acetoxycyclohexanone can also be accomplishedin one step by treatment with t-butylhydroperoxide and catalytic amountsof molybdenum hexacarbonyl in refluxing benzene.

The following examples furtherillustrated the invention but are not tobe construed as limitations thereof.

EXAMPLE I This example illustrates the preparation of the 2-acetoxyeyclohexanone. V I I Into a 200 mls. flask equipped with amagnetic stirrer, heating mantle and condenser, there were charged 98.0grams of cyclohexanone, 294 grams acetic anhydride and 6.0 grams ofconcentrated (96 wt. percent) sulfuric acid. The resultant mixture wasrefluxed for a period'of 2 hours and the resultant formed1-cyc1ohexenylacetate in an amount of 127.0 grams representing 91 wt.percent yield was recovered by quenching the mixture in 200 mls. of icewater, stirring for 10 minutes, then extracting with four 100 mls.portions of ether, the ether extract layers were combined, dried andfractionally distilled. Ether was recovered at atmospheric pressure andl-cyclohexenylacetate recovered at reduced pressure.

Subsequently, into a 200 ml. flask equipped with a magnetic stirrer, aheating mantle and condenser, there were charged 5 grams of the formedl-cyclohexenylacetate, 100 grams of benzene, 0.05 grams molybdenumhexacarbonyl and 8 grams of 79 wt. percent tertiary butyl hydroperoxide.The reaction mixture was heated to reflux (80 C.) for 10 hours andworkup of the reaction was as follows:

The reaction mixture was cooled to about 10 C. The catalyst was filteredout and the solution was distilled to give benzene and t-butyl alcoholat atmospheric pressure and reaction starting material and product atreduced pressure. There were recovered 3.41 grams ofZ-acetoxycyclohexanone.

EXAMPLE II This example illustrates the method of the invention and theadvantages thereof.

Into a 200 mls. 3-necked flask equipped with a magnetic stirrer, gassparger, a condenser and thermometer, there were chargedZ-acetoxycyclohexanone (as prepared in example 1), acetic anhydride (AcO), acetic acid (HOAc) (in preferred run A) and boron trifluorideetherate (BF -Et o). The reaction mixture was heated to reflux while drynitrogen was passed through at a rate of 140 mls. per minute. Themixture was then cooled to about 10 C. and concentrated (96 wt. percent)sulfuric acid was added slowly so the temperature remained below aboutC. The reaction mixture was heated and at the end of the reaction periodthe formed catechol diacetate product was recovered by the followingwork-up:

The reaction mixture was added to 100 mls. of ice water and stirred forone-half hour to decompose the excess AC O. It was then extracted withthree 50 mls. portions of ether. The ether layers were combined andwashed with two 50 mls. portions of saturated sodium bicarbonate aqueoussolution (about 7 percent wt. of NaHCO once with 50 mls. of saturatedaqueous solution of sodium chloride, dried and the ether distilled togive a residue which upon distillation under vacuum affords catecholdiacetate.

The test data and results are reported under runs A, B and C in table 1below. In addition, comparative runs D, E and F were made.

TABLE I Run A B C 1) E F Reaction ingredients:

Acetoxy cyclohexanone, g 4.1 4. 1 4.1 4.1 4. 4. l BF;.Et10,g 0.9 0.0 0.90.9 0.0 H:S04,g 5.2 5.2 5.2 5.2 5. Aci0,g 30.0 50.0 50.0 50.0 30.0HOA0,g 30.0 30.0 30

Reaction conditions:

Stage I:

l catechol diacetate. 1 Only 1, Z-diacetoxycyclohex-lene was obtained.

1 claim: 1. A method of preparing catechol diacetate of the formula:

W ()0 CHa R 0 E C H; 11:...

where R, R, R and R are hydrogen or alkyl of from one to 20 carbonscomprising first contacting a Z-acetoxycyclohexanone of the formula:

OCCHa where R, R R and R are as heretofore defined with a mixture ofboron trifluoride etherate, acetic anhydride at a first temperaturebetween about 30 and 500 C., utilizing a first mole ratio of said aceticanhydride to said acetoxycyclohexalone of at least about 1:1 saidetherate present in an amount between 0.1 and 10 wt. percent of thefirst reaction mixture, subsequently second contacting said firstreaction mixture with concentrated sulfuric acid at a second temperaturebetween about 30 and 500 C., utilizing a second mole ratio of saidsulfuric acid to said acetoxycyclohexanone of at least about 0.05:].

2. A method in accordance with claim 1 wherein said first and secondcontacting are conducted in the presence of an 1

2. A method in accordance with claim 1 wherein said first and secondcontacting are conducted in the presence of an inert gas atmosphereunder conditions of agitation.
 3. A method in accordance with claim 1wherein said first mole ratio is between about 5:1 and 20:1, said secondmole ratio is between about 1:1 and 2:1, said first and secondtemperature is between 80* and 150* C., said first contacting conductedin the additional presence of between about 30 and 70 wt. percent aceticacid basis said first reaction mixture.
 4. A method in accordance withclaim 1 wherein R1, R2, R3 and R4 are hydrogen.